The U.S. Postal Service will move this month toward reducing mail delivery from six days a week to five, a change Postmaster General John Potter has said is critical to reducing its massive debt.

Potter said Monday he’ll submit a formal request by the end of this month to the Postal Regulatory Commission, which must issue an advisory opinion on any change in mail service that would have national impact.

“We know we’re going to have less mail in 2020 than we have today,” Potter says. “We can’t freeze wages. We can’t freeze fuel costs.”

Once Potter makes the request, the Postal Regulatory Commission will hold public hearings in Washington and around the USA and seek expert testimony, Commission Chairwoman Ruth Goldway said.

“The Postal Service is an enormous organization. This change in service that they’re proposing is a very complex and significant change,” Goldway said. “The Postal Service is an essential part of the country’s infrastructure, so you don’t want to change it willy-nilly.”

Even if the independent commission approves the dropped day, the Postal Service also needs congressional consent. Federal law requires six-day delivery.

Potter raised the issue last year in testimony before a House oversight subcommittee. Rep. Stephen Lynch, D-Mass., chairman of the subcommittee that oversees the Postal Service, said then that other cost-saving measures should be considered before cutting delivery.

As more people communicate and pay their bills online, Postal Service projections show Americans in the next decade will send significantly less mail than they do now, reducing revenue while labor and fuel costs increase. Potter will release the details today of a $4.8 million study that projects how steeply mail volume will fall and how deeply the Postal Service will be in debt by 2020. The Postal Service delivered about 177 billion pieces of mail in 2009.

The Postal Service has already borrowed $10 billion from the U.S. Treasury. Potter says it expects to borrow another $3 billion this year, leaving it just $2 billion under the $15 billion cap set by Congress.

Potter also will ask the regulatory commission to reconsider requiring the Postal Service to set aside money for future retiree health care benefits.

The commission is concluding hearings on a Postal Service proposal submitted in July to close and consolidate 154 post offices throughout the USA, Goldway said. The commission expects to issue its advisory opinion in the next two weeks.

“The Postal Service is nervous about its financial conditions and is making a lot of broad proposals,” she said. “Some of the proposals, when they see the light of day may be very worthwhile.”